1. Field of the Invention
The present invention relates to a method for realizing gray levels of a liquid crystal display (LCD) device, and more particular to a method for realizing gray levels of an LCD device, which realizes the gray levels by interworking a gamma voltage and a sub-frame.
2. Description of the Prior Art
As generally known in the art, a liquid crystal display (LCD) device has a liquid crystal layer formed between an upper substrate including a color filter and a lower substrate spaced from the upper substrate with a predetermined distance. A background light source is under the lower substrate. In this LCD device, a voltage having a predetermined intensity is applied to the liquid crystal in order to adjust a liquid crystal layer transmission rate of the background light source according to the degree of twist of the liquid crystal, so that a user can obtain a desired image signal. Herein, in order to obtain the image signal, a data voltage including image information in the form of a gray level is applied to the liquid crystal. According to realization types, the LCD device is classified into an LCD device employing a color filter scheme in which R, G, and B color filters are formed on the upper substrate and white light is transmitted through the substrate, so that the image signal is obtained and an LCD device employing a Field Sequential Color (FSC) scheme in which each of R, G, and B light is transmitted through a substrate, so that the image signal is obtained.
A method for realizing gray levels in a LCD device includes a scheme in which a reference gamma voltage is set in a control board and a gamma curve is adjusted using a resistor string in a source driver and a digital operation scheme enabling the realization of the gray levels through an on/off operation at a plurality of sub-frames.
In the scheme of adjusting the gamma curve using the resistor string in the source driver, N reference voltages set in an external buffer are employed as the reference gamma voltages in the source driver. The source driver sets a voltage of each detailed gray level using an R-string circuit, thereby realizing gray levels by means of a D/A converter and an internal buffer. In the digital operation scheme, one frame is divided into plural sub-frames, and digital data is input to each sub-frame and the sub-frames are on/off driven, thereby realizing a gray level.
However, in the scheme of adjusting the gamma curve using the resistor string in the source driver, it is necessary to install a D/A converter and a buffer in a driver IC (source driver) in order to realize each gray level, so that the size of the driver IC may increase. Also, in the digital operation scheme, since liquid crystal is charged/discharged correspondingly to the number of the sub-frames, a high-speed driver IC is required and power consumption increases according to the high speed operation of the driver IC.